This invention relates to an improvement in preventing loosening of a stencil, and more particularly relates to a stencil which is tightly wound in the shape of a roll and is used for a printing machine such as a stencil printer, and to a stencil perforating device which can detect a feeding direction of the stencil roll loaded therein, and automatically or semi-automatically pays the leading edge of the stencil from the stencil roll.